1. Field of The Invention
This invention generally relates to a communication device connected to a packet switching network and more particularly to what is called a communication-tracing-information processing device.
2. Description of The Related Art
Generally, the state of a communication system is constantly "traced" (namely, data representing the current state of the communication system is constantly recorded) with the intention of analyzing the cause of a communication fault occurring therein and of preventing a recurrence of such a communication fault. Similarly as in case of a recorder used for an analysis of an air accident, there is a limit to the storage capacity of a device for storing communication data (hereunder sometimes referred to as tracing data) obtained as a result of performing a tracing the state of the communication system. Thus, if tracing data to be stored excesses the storage capacity of the device, the excess tracing data is sequentially overwritten to the storage area, in which the tracing data previous to the excess tracing data has been stored, of the device. Consequently, the device usually stores a fixed magnitude or size of tracing data.
Referring now to FIG. 3, there is schematically shown the configuration of a conventional communication device of such a type. In this figure, reference numeral 11 designates a communication portion for performing a communication processing to communicate with a packet switching network. As is shown in this figure, the communication portion 11 comprises a physical-layer processing part 7 for performing a processing of first-layer (or physical-layer) protocols of layered communication protocols, a link-layer processing part 8 for performing a processing of second-layer (or link-layer) protocols thereof, a network-layer processing part 5 for performing a processing of third-layer (or network-layer) protocols thereof and an upper-layer processing part 3 for performing a processing of layers, the order of which is higher than third layer thereof, and a communication tracing information processing portion 14. Further, reference numeral 12 denotes a storage portion for storing communication-tracing-information; and 18 a pointer portion for storing a pointer used to manage memory addresses in the storage portion 12.
Hereinafter, an operation of the communication-tracing-information processing portion 14 will be described by referring to FIG. 4. First, in step ST11, the communication-tracing-information processing portion 14 fetches a pointer from the pointer portion 18 at the time of a transmission or reception of data. Then, the communication-tracing-information processing portion 14 writes data respectively representing time and the transmission or reception to the storage portion 12 from an address indicated by the pointer updating the pointer in step ST12. Subsequently, in case of the transmission, the communication-tracing-information processing portion 14 inputs transmission data having a format of FIG. 5 from the upper-layer processing part 3 and then writes bytes of a necessary number of the transmission data to the storage portion 12 from a leading byte thereof in step ST13, updating the pointer. Further, in case of the reception, the communication-tracing-information processing portion 14 inputs reception data from the network-layer processing part 5 and then writes bytes of a necessary number of the reception data to the storage portion 12 from a leading byte thereof in step ST13, updating the pointer. Upon completion of the writing of the transmission or reception data to the storage portion 12 in step ST13, the updated pointer is saved in the pointer portion 18 in step ST14. In this way, communication-tracing-information having a format of FIG. 6 is sequentially stored in the storage portion 12. Incidentally, when data is written to the last address of the storage portion 12, the pointer is changed in such a manner to indicate the leading address of the storage portion 12. The subsequent communication-tracing-information is written over the information stored in the storage portion from the leading address thereof.
When a communication fault occurs in a system employing this conventional communication device, the communication-tracing-information stored in the storage portion 12 as above described is used for an analysis of the cause of the fault.
However, the conventional communication device having the above described configuration, in which communication-tracing-information is simply written to a storage area in the order of occurrence of corresponding transmission or reception data, has a drawback in that it is not seldom to fail to obtain sufficient communication-tracing-information required for an analysis of a communication fault. This is due to the fact that communication-tracing-information is simply written to a storage area or portion, the storage capacity of which is limited, in the order of occurrence of corresponding transmission or reception data and thus communication-tracing-information relating to the communication fault is often lost by overwriting communication-tracing-information corresponding to a subsequent transmission or reception.
Incidentally, the frequency of losing communication-tracing-information relating to a communication fault can be reduced by increasing the storage capacity of the storage portion. The conventional communication device, however, comes to have other drawbacks as follows. Namely, increase in storage capacity inevitably results in increase in cost of the storage portion and is thus uneconomical. Moreover, increase in communication-tracing-information stored in the storage portion makes a search for communication-tracing-information necessary for an analysis of a communication fault very difficult and is liable to increase a time required to analyze a communication fault.
The present invention is accomplished to eliminate the drawbacks of the conventional communication device.
It is, accordingly, an object of the present invention to provide a communication device which can obtain communication-tracing-information necessary for an analysis of a communication fault more surely without increasing the storage capacity required to store communication-tracing-information.
Further, it is another object of the present invention to provide a communication device which can store communication-tracing-information in a storage portion correspondingly to each logical channel and save communication-tracing-information in another storage device each time a communication fault occurs, thereby surely holding existing data at the time of an occurrence of a communication fault and saving the data in the order of occurrences of corresponding communication faults to facilitate analyses of the communication faults.